The invention relates to an electric motor comprising a device for generating a sequence of signals.
In the case of modern electric motors, the power output, revolutions per minute, speed and acceleration are regulated or controlled by motor control units. In so doing, the electric motors are controlled via electric switches which are switched into a conducting or blocking state as a function of the position and the desired movement of a rotor. Furthermore, electromagnetic energy is radiated via the electric switches when generating signals, in particular for actuating an electric motor. In addition, the cables which conduct signals operate in accordance with an antenna and induce an electromagnetic radiation.
Electric motors for driving a fan have a constant speed over extended periods of time, which is achieved by a constant sequence of control signals. The electric switches are thus switched at a constant frequency. The entire electromagnetic radiation occurs at few frequencies or respectively in a limited frequency range.
An electric motor comprising a device for generating a sequence of signals is known, wherein the sequence of signals comprises a plurality of signal blocks and the signal blocks comprise a plurality of signals having a specific signal duration. It is also known that the signals themselves can be configured as a pulse, wherein each pulse comprises a different energy content depending on the pulse width or corresponds to an item of information. Such a signal is referred to as a pulse-width modulated signal.
It is furthermore known that it is possible to vary the width of the pulses by means of random lengthening or shortening during a pulse-width modulation, wherein the signals consist of a square wave pulse. The variation of the pulse widths results in an increase in the number of switching frequencies. An increase in the number of switching frequencies leads to the radiated energy being distributed across the individual switching frequencies, referred to below as frequency spreading. In order to evenly distribute the energy, the variation of the pulse width must occur randomly. If the variation of the pulse occurs randomly, it is therefore not possible to reproduce or respectively determine the original pulse width and accordingly the actual information of the pulse.